It is generally known that the combustion process within an engine produces noxious oxides of nitrogen (NOx), which causes undesirable results, such as pollution. The presence of NOx in the exhaust gas of internal combustion engines is generally understood to depend upon the temperature of combustion within the combustion chamber of an engine. To control the emissions of unwanted exhaust gas constituents from internal combustion engines, it is known to re-circulate a portion of the exhaust gas back to an air intake portion of the engine. Because the re-circulated exhaust gas effectively reduces the oxygen concentration of the combustion air, the flame temperature at combustion is correspondingly reduced, which decreases the emissions of NOx since the NOx production rate is exponentially related to flame temperature.
It is further known to cool the re-circulated exhaust gas prior to introducing the gas at the engine air intake port. Thus, an EGR cooler is typically arranged within the exhaust gas recirculation system to cool the stream of re-circulated exhaust gas. The temperature of the exhaust gas exiting from the cooler is critical both to the NOx control process and to the integrity of the cooler and the downstream components, such as EGR conduits, EGR flow control valves, and the engine.
However, next generation emission standards will require lower intake manifold temperatures. In order to meet these standards, a new approach to EGR-cooler-coolant plumbing is needed. The present invention addresses such a need.